The correct answer is D) The size and number of major US cities increased.
The major population trend that occurred in the US during the Industrial Revolution was "The size and number of major US cities increased."
With the advent of the Industrial Revolution, many things changed. Indeed, the Industrial Revolution changed the life of many people.
Farmers that used to work in their farm fields decided to leave the rural areas of the country to move to the larger cities where the big industries and factories were located. Immigrants also arrived because they were looking for better living conditions.
That is why the larger cities saw an increase in population. These workers labored for long hours under unhealthy conditions and lived in overcrowded spaces where disease quickly spread.